As substrates for use in fabrication of very highly integrated semiconductor devices, mirror-polished silicon wafers are mainly used. These silicon wafers are produced by growing a silicon single crystal ingot according to the CZ method (the Czochralski method) and machining the grown single crystal ingot into wafers. In single crystal manufacture by the CZ method, the increasing size of apparatus and its furnace parts has been brought about by the increasing diameter of silicon wafers to reduce fabrication cost of semiconductor devices.
In the CZ method, a polycrystalline raw material charged in a quartz crucible is heated with a cylindrical graphite heater, and a single crystal is grown from the resulting silicon melt. The increasing size of crucibles and the like accompanying the increasing diameter of single crystal ingots being grown as above has increased also the size of heaters that surround and heat the crucibles. This makes a problem in that an electric discharge occurs due to contact with other components caused by heater deformation such as deflection. The weight of a larger heater may cause the deformation. Particularly, in the MCZ method (the magnetic field applied Czochralski method), Lorentz force in a magnetic field may also cause the deformation, and this cannot be ignored. To prevent the heater deformation, a method of providing auxiliary electrodes other than heater electrodes to support the heater has been used (See Patent Document 1).